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Old 30th January 2006, 10:22 PM   #1
4real is offline 4real  Netherlands
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Question Small multi-UcD for active speaker setup, what to do?

Hi there,

At the moment, I was planing on using several different amps to power my future active speaker setup. But I'm afraid it's going to be a big mess.

So, a new idea: take 6 UcD amps and put them into a 2U 19" case. 2U because I want to keep it as small as possible 3U is absolute max.

Next problem: how to het 6 amps and power supplies into one case? Obviously there is no way to cramp 6 transformers and power supplies into one such case.

So I thought: one huge 1000 VA transformer will do. Put a big 3x33.000 uF (or a bit more) (per rail) PSU behind it, and I'll be fine?

Next problem: I intend to use two UcD400's for my low frequency section, and four UcD180AD's for the mid's and high's. Since they will all get the same voltage, I'm need to choose a voltage that both amps will work with: I guess about 50V DC will do: so I need a 35V 1000VA tranformer.

All of this should be able to fit inside the case.

But now my questions:

- Will this me any good?
- Are there any better options?
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Old 31st January 2006, 12:01 PM   #2
Pano is online now Pano  United States
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I'm a little surprised you haven't gotten any answers yet. Where is the UCD clan?

I'm not a UCD guy, but I'm not shy about giving an opinion, so here it is:

You seem to have given this some thought, thatís good. I do believe it could work well, but there are some problem areas that you should watch out for.

1) Noise. There will be a lot of power running around in this case, both the typical 50/60 Hz and all the switching RF. Good grounding and good shielding will be important. With 6 channels, you have a plenty of places to pick up noise.
I don't know how bad the Hypex modules are at radiating and picking RFI, but there is bound to be a lot of it in the case, with 6 modules. You may have to build metal walls between them. UCD guys?

2) Gain structure. From your post it sounds like you will be using a 3 way active filter in front of the amps. Gain structure will be important. You don't want to heavily attenuate the signal at one place only to greatly amplify it later in the chain. That leads to bad SNR and distortion.
In pro audio getting your gain structure right is 1/2 the battle. A lot of guys don't. The same applies to Hi-Fi, especially since you will have a complicated system. Do some planning and thinking about this, it's important.

3) Power supply. Ideally each module would be in its own case with its own supply, but I can understand why you would not want to do that. Using just one transformer, there is no reason not to break up the supply after that point. I.E., a separate rectifier bridge and filtering for each module.
If there is not room for 6 separate subsystems like that, you could combine and use 3 or 2. You'll get more PSU crosstalk, but maybe not enough to hurt. You'll have to decide if you want to separate left/right to different supplies (2) - or do you want to separate Hi-Mid-Lo? (3) My feeling would be to separate Hi-Mid-Lo, as there is often much more signal difference between the frequency bands than there is between left and right
Don't neglect the power to the mids, they need more power than most people think. There is a lot of energy in the mid band.

OK, that gives you something to think about. Hopefully some of "Clan UCD" will jump in and take you further.

Good luck with the project!
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Old 31st January 2006, 12:37 PM   #3
4real is offline 4real  Netherlands
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Many thanks for your response. Any input is very welcome!

Quote:
Originally posted by panomaniac
1) Noise. There will be a lot of power running around in this case, both the typical 50/60 Hz and all the switching RF. Good grounding and good shielding will be important. With 6 channels, you have a plenty of places to pick up noise.
I don't know how bad the Hypex modules are at radiating and picking RFI, but there is bound to be a lot of it in the case, with 6 modules. You may have to build metal walls between them. UCD guys?
Yes, I was panning on giving amps PSU and transforer seperate "compartments". transformer and PSU in the middle, and three amps on either side, and six LED's on the front panel

Quote:
2) Gain structure. From your post it sounds like you will be using a 3 way active filter in front of the amps. Gain structure will be important. You don't want to heavily attenuate the signal at one place only to greatly amplify it later in the chain. That leads to bad SNR and distortion.
In pro audio getting your gain structure right is 1/2 the battle. A lot of guys don't. The same applies to Hi-Fi, especially since you will have a complicated system. Do some planning and thinking about this, it's important.
No, after the filter (actually an PC+soundcard ), there will be an active volume control (probably some PGA volume controlled stuff), so I can use the full potential of my available DAC's dyanamic range. It might even be nice to build this into the amp if there is any room left. But a seperate one would be best in the light of expansion

Quote:
3) Power supply. Ideally each module would be in its own case with its own supply, but I can understand why you would not want to do that. Using just one transformer, there is no reason not to break up the supply after that point. I.E., a separate rectifier bridge and filtering for each module.
If there is not room for 6 separate subsystems like that, you could combine and use 3 or 2. You'll get more PSU crosstalk, but maybe not enough to hurt. You'll have to decide if you want to separate left/right to different supplies (2) - or do you want to separate Hi-Mid-Lo? (3) My feeling would be to separate Hi-Mid-Lo, as there is often much more signal difference between the frequency bands than there is between left and right
Don't neglect the power to the mids, they need more power than most people think. There is a lot of energy in the mid band.
Yes, I was also thinking of separating the PSU's, but was not sure how to do it channel wise. I guess keeping left/right seperate seems logical... About power: Since thy will all use one transformer, power will always be there where it's needed, and 1kVA should be enough I guess. With seperate PSU's you'll need to make sure the CPU capacity is well matched between the amps for it's purpose. Lot's for bass, a bit less for mids, and the high get the least.
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Old 31st January 2006, 12:42 PM   #4
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Why do you want to use two different models of UcD ? Since you intend to feed both with the same supply voltage they will give the same output power independant of type.

Regards

Charles
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Old 31st January 2006, 01:38 PM   #5
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by phase_accurate
Why do you want to use two different models of UcD ? Since you intend to feed both with the same supply voltage they will give the same output power independant of type.

Regards

Charles

I agree, that is why I plan to use all UcD400 modules even for mid and tweeter although that is pure overkill. Putting 6 modules in one case including power supplies will be a tough job I think. My advise is to use one case for each channel (left and right) and put 3 amps in each case with one supply for the 3 amps and use the same modules either UcD400 or UcD180 for all amps. Another solution costing maybe a bit more is to use a UcD400 for the woofer with its own supply and transformer and using UcD180 for mid and tweeter with one supply + transformer for the UcD180 modules. That way you keep the supply voltage of the mid and high amps cleaner as that supply will not be drained by the more power demanding woofers.

Best regards

Gertjan
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Old 31st January 2006, 01:39 PM   #6
4real is offline 4real  Netherlands
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That's true, but the price difference is very small, and it will leave me with a bit more overhead and room to upgrade if I want to.
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Old 31st January 2006, 01:44 PM   #7
Pierre is offline Pierre  France
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Have you thought about the possibility of using one or two swithmode power supplies? That would give you a lot of free space and also a drastic weigth reduction.

Not easy to find, that's true, but there are some of them out there
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Old 31st January 2006, 01:47 PM   #8
4real is offline 4real  Netherlands
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Yes, I found some that might be usable, but they are very expensive, and will not take the need for the capacitors away (maybe less of them). So effectively, I will not gain anything in term of space.

I also thought about ging the UcD400's a seperate power supply and transformer. But I'll have to check if that would fit..
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Old 31st January 2006, 01:51 PM   #9
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Hi,

I was thinking the same actually, only reason I could think of was the 400's having more current capability if the woofers are more demanding.

Furthermore 50 volts is I think far too high for the UCD180's, their overvoltage trips at ~52 volts, you need to allow for a mains overvoltage of 10% + say another 5% for idle/unloaded conditions.

You really wouldn't want your mids and highs to kick out while the bass keeps going, kind of annoying.

1000VA seems to me to be anemic as well, for six modules. Would be better to have 1000VA for the subs and another 1000VA for mids and highs, case size be damned. You can also run the subs in bi-phase with ease to share the PSU better.

I trust with the level of capacitance you have in mind that you're talking about 8ohm loads? Hope so.

It would of course be best if you can build each module into their own little shielded cages but it likely isn't necessary either.

Regards,
Chris
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Old 31st January 2006, 01:58 PM   #10
4real is offline 4real  Netherlands
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Quote:
Originally posted by classd4sure
Furthermore 50 volts is I think far too high for the UCD180's, their overvoltage trips at ~52 volts, you need to allow for a mains overvoltage of 10% + say another 5% for idle/unloaded conditions.
That's very true . So I guess I must split the two (low and mid/high).

Quote:
1000VA seems to me to be anemic as well, for six modules. Would be better to have 1000VA for the subs and another 1000VA for mids and highs, case size be damned. You can also run the subs in bi-phase with ease to share the PSU better.
It's not as if I'm planing om blowing up something here 2 kVA for the whole lot is a bit much. It's just for two speakers, remember . If I get 300W out of the UcD400's I'll be pleased. So a 625 VA will do. For the mids and highs I guess the same will also do I guess.

Also note that the woofers are 94 dB each (I will have two per side). Even though they will be in a dipole config, I will not need that much power to get them moving

Quote:
I trust with the level of capacitance you have in mind that you're talking about 8ohm loads? Hope so.
Nope, woofers will be somewhere about 4 Ohms, mid wil be 8, and tweeter will be 6 Ohms. Would you suggest more capacitance?

@all: Many thanks already for the great sugestions!
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